It is no secret that smoking increases the risk for cancer, heart disease, diabetes and even blindness. But puffing on a cigarette is not associated with a higher risk of dementia, says a new study.
The present study, published in the Journal of Alzheimer’s Disease, stands in contrast to the previous research that found a correlation between smoking and dementia.
“The underlying data (in those studies) was solid, but the analysis didn’t take into account the idea of competing risk of mortality, which we felt was an important factor to consider in this case since smoking is so strongly associated with earlier death,” Erin Abner from University of Kentucky, who was among the the researchers, said.
For the study, the researchers included 531 initially cognitively-normal people.
They used a statistical method called competing risk analysis to determine whether there was a connection between smoking and dementia.
The data demonstrated that smoking was associated with a risk of earlier death — but not dementia.
“While our study results could influence smoking cessation policy and practice, we feel that the most important consequence of our work is to demonstrate how this method could change the way we approach dementia research and to advocate for its adoption in the appropriate areas of study,” said Abner.
Researchers have revealed that living near a major road or highway is linked to higher incidence of dementia, Parkinson’s disease, Alzheimer’s disease and multiple sclerosis (MS).
For the findings, published in the journal Environmental Health, researchers from the University of British Columbia analysed data for 678,000 adults in Metro Vancouver.
They found that living less than 50 metres from a major road or less than 150 metres from a highway is associated with a higher risk of developing neurological disorders — likely due to increased exposure to air pollution.
“For the first time, we have confirmed a link between air pollution and traffic proximity with a higher risk of dementia, Parkinson’s, Alzheimer’s and MS at the population level,” said study lead author Weiran Yuchi from the University of British Columbia in Canada.
Neurological disorders, a term that describes a range of disorders, are increasingly recognised as one of the leading causes of death and disability worldwide.
Little is known about the risk factors associated with neurological disorders, the majority of which are incurable and typically worsen over time.
For the study, researchers analysed data for 678,000 adults between the ages of 45 and 84 who lived in Metro Vancouver from 1994 to 1998 and during a follow-up period from 1999 to 2003.
They estimated individual exposures to road proximity, air pollution, noise and greenness at each person’s residence using postal code data.
During the follow-up period, the researchers identified 13,170 cases of non-Alzheimer’s dementia, 4,201 cases of Parkinson’s disease, 1,277 cases of Alzheimer’s disease and 658 cases of MS.
For non-Alzheimer’s dementia and Parkinson’s disease specifically, living near major roads or a highway was associated with 14 per cent and seven per cent increased risk of both conditions, respectively.
When the researchers accounted for green space, they found the effect of air pollution on the neurological disorders was mitigated.
The researchers suggest that this protective effect could be due to several factors.
“For people who are exposed to a higher level of green space, they are more likely to be physically active and may also have more social interactions,” said study senior author Michael Brauer.